Hi Oliver,
The U- family of fonts are created when groff is built IF it can find
the URW fonts in specific places on the system (there is also a way to
tell configure to find them yourself). If you compile your groff from
source just make sure you have installed the URW fonts before running
the configure command and make sure it reports the URW fonts have been
found. If you are using a packaged version of groff where it has been
decided not to use these alternative fonts you could use Peter
Schaffter's script to install new fonts which do contain this glyph.
His site says:-
"A bash script to make the entire process of installing fonts a
painless no-brainer has been posted online at
http://www.schaffter.ca/mom/install-font . Be sure to make the script
executable ( chmod 755 install-font ) after you download it, then type
./install-font -H for usage."
Cheers
Deri